What's your favorite brand of chocolate to use when making truffles?
I religiously use Valharona when I can afford it, when I can't, I use Trader Joes. It's not a crazy difference, but I like TJ's above most other budget friendly options.
Ditto what JessieLK says. Valhrona's the bomb, but TJ's dark chocolate comes really, really, really close.
If you have the time, order the chocolate discs from Jacques Torres: http://www.mrchocolate.com/proddetail.php?prod=1poundbulkbag
It might be all in my head, but I swear his chocolate melts best, is the easiest to work with, has just the right semi/bitter-sweetness, plus, your friends will think you're way cool when you name-drop. His chocolate is $9.50 per pound plus shipping, not bad when you consider "good" chocolate retails here for $12 to $16 a pound, not including shipping.
If your truffles will contain only chocolate and cream, splurge for Jacques Torres, Valrhona, Scharffen Berger or Callebaut. I'm not one of those people who can detect floral notes or oak or coffee or burnt undertones in my chocolate, but I think "good" chocolate makes all the difference in a recipe so simple.
European brands tend to be creamier and more chocolate-y than American brands because European manufacturers roast beans at a lower temperature for a longer period of time, which helps to develop flavor. Most American manufacturers roast beans at higher temperatures for a shorter time, resulting in a flavor that's not so smooth, so they add more sugar to compensate. (I'm not sure where Jacques Torres roasts his beans, but I'd bet they're made in America the European way, like Scharffen Berger is.)
That said, I will also tell you that I've made very good truffles with Ghirardelli and Nestle Toll House morsels.
If you will be adding butter or vanilla or mint to your truffles, or if you plan to coat them in cocoa or enrobe them in melted chocolate, you will need to determine if your chocolate will pair well with these other flavors. I would be more than happy to assist you in conducting a taste test--if you buy the chocolate, I'll do the tasting.
I'll give a vote for Scharffen Berger as well, but when I don't want to pay quite that much, I'll go with Theo Chocolate. Their Madagascar single-origin bar is especially flavorful with lovely cherry and apricot notes that really come through when combined with cream. It's my favorite for a simple ganache. Their Costa Rica bar is also delicious: darker than the Madagascar, with a light nuttiness balanced against smooth fruity undertones.
I really like cooking with Callebaut bittersweet and semi-sweet baking bars. If you buy the big bars they aren't too expensive compared to Valrhona or Sharffenberger. They melt easily, and give a beautiful texture to truffles. The flavor is straightforward and chocolate-y--I find that a lot of single-origin chocolates have interesting layered flavors, but not necessarily ones that you'd want in a truffle.
Thank you all for your recommendations! I'll keep Valhrona & Scharffen Berger in mind for when I'm ready to splurge, but for my first truffle try, I'm going with betteirene's Mrchocolate.com recommendation. (There are no Trader Joe's where I live, which is something that saddens me for many reasons.) It's also reassuring to know you can make good truffles with regular grocery store chocolate, in a pinch. For this truffle trial, I'll try to take the flavor up a level. Thanks again!